Copper for delivery in September rose 1% from Thursday’s settlement price, touching $4.431 per pound ($9,748 per tonne) on the Comex market in New York.

Copper prices have soared to record highs this year, handing unions in Chile additional leverage, ratcheting up tensions in labor negotiations and putting pressure on global supply of the red metal.

On Thursday, two unions at Andina walked off the job after rejecting the latest contract offer, while workers at JX Nippon Copper’s Caserones mine also went on a strike after labor contract talks collapsed.

Andina produced 184,000 tonnes of copper in 2020, while Caserones delivered 126,972 tonnes of copper in 2020.

On Thursday, workers at Chile’s Escondida mine, the world’s biggest copper deposit, approved a new contract, avoiding a labor strike.